Fiber-cement/gypsum laminate composite building material

ABSTRACT

A building material ( 40 ) is provided comprising fiber-cement ( 10 ) laminated to gypsum ( 20 ) to form a single piece laminate composite. This single piece laminate composite exhibits improved fire resistance and surface abuse and impact resistance, but achieves these properties without the excessive weight and thickness of two piece systems. Additionally, because of the reduced thickness, the preferred laminate building material is easier to cut and is quicker and easier to install than two piece systems. Furthermore, forming the fiber-cement and gypsum into a single piece laminate eliminates the need to install two separate pieces of building material, thereby simplifying installation. In one embodiment, a ⅝″ thick laminate composite is provided comprising a ½″ thick gypsum panel laminated to a ⅛″ thick fiber-cement sheet, the laminate composite having a fire resistance rating of 1 hour when measured in accordance with ASTM E119.

[0001] This application is a continuation of prior U.S. application Ser.No. 09/685,637, filed Oct. 10, 2000 and also claims the benefit ofProvisional Application Serial No. 60/158,600, filed Oct. 8, 1999.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] This invention relates to abuse resistant, impact resistant andfire resistant building materials, and more particularly, to a singlepiece laminate composite building material of fiber-cement and gypsum.

[0004] 2. Description of the Related Art

[0005] The interior wallboard market has been dominated by the use ofgypsum wallboard products for many years. The gypsum wallboard typicallycomprises thin paper layers wrapped around a gypsum core. For example,one paper layer covers the face and long edges of the board, and thesecond paper layer usually covers the back surface of the board. Thecore is predominantly gypsum, and can be modified with additives such asglass fiber, vermiculite and mica to improve fire resistance.

[0006] In addition to fire resistance, abuse resistance is anotherdesired quality in wallboards. Gypsum has poor abuse resistance comparedto other wallboard materials such as wood or masonry. The paper surfaceof gypsum wallboard is easily damaged by impact such as scuffing,indentation, cracking or penetration with hard or soft body objects suchas furniture, trolleys, toys, sports equipment and other industrial orresidential furnishings. Such wall abuse is typical in high trafficrooms such as corridors, family living areas, gymnasiums or changerooms.

[0007] Gypsum wallboard manufacturers have made modifications to theirgypsum wallboards to improve their abuse resistance. One method was tobond a plastic film to the back of the wall panel to resist penetrationof the impact bodies into the framed wall cavity. Another method was tomake a fiber-gypsum wall panel with fiber-gypsum outer layers formedonto a gypsum-based core. These products typically have improved surfaceabuse resistance to the paper surface of normal gypsum wallboard.Similar gypsum-based or cement gypsum-based compositions are typicallydescribed in U.S. Pat. Nos. 5,817,262 and 5,718,759.

[0008] One material having significant abuse resistance is fiber-cement.Fiber cement has an advantage over gypsum panel with respect to surfaceabuse resistance such as wear and abrasion. One disadvantage of fibercement by itself as a wall panel is that it does not have a fireresistance rating comparable to gypsum wall panels of equal thickness.Another disadvantage of fiber cement by itself is that it issignificantly heavier than gypsum wall panels of equivalent thickness.For example, a 1 hour fire resistance-rated wall system with fibercement requires mineral insulation in the wall cavity or a sub-layer offire rated gypsum wall panel to achieve a 1 hour fire resistance ratingwhen tested in accordance with ASTM E-119.

[0009] A 2-layer system of ¼″ fiber cement over ⅝″ type X fire ratedgypsum wallboard has been used to achieve both fire resistance and abuseresistance. Such a system is described in Gypsum Association—FireResistance Design Manual—GA FILE NO. WP) 1295—Gypsum wallboard, steelstuds, fiber-cement board proprietary system. This two piece system isdisadvantageous because it is significantly heavier than single-layergypsum wallboards. Additionally, the 2-layer wallboards require nearlydouble the amount of labor for installation because two separate wallpanels must be installed instead of a single panel. Also, the extrathickness of the 2-layer systems (⅝″+¼″=⅞″) is not compatible with mostdoor jamb widths.

SUMMARY OF THE INVENTION

[0010] Accordingly, what is needed is a single piece building materialthat has good abuse resistance, impact resistance and fire resistance.This building material should also be light, easy to manufacture andcompatible with standard building material sizes. With respect to fireresistance, it would be especially advantageous for such a material tohave a fire resistance rating of at least one hour as measured by ASTME119.

[0011] Briefly stated, the needs addressed above are satisfied in oneembodiment by a building material comprising fiber-cement laminated togypsum to form a single piece laminate composite. This single piecelaminate composite exhibits improved fire resistance and surface abuseresistance, but achieves these properties without the excessive weightand thickness of two piece systems. Additionally, because of the reducedthickness, the preferred laminate building material is easier to cut andis quicker and easier to install than two piece systems. Furthermore,forming the fiber-cement and gypsum into a single piece laminateeliminates the need to install two separate pieces of building material,thereby simplifying installation.

[0012] One object of the invention is to provide a building boardproduct suitable for applications requiring surface abuse resistance,improved impact resistance and a 1-hour fire resistance rating (asmeasured, for example, by ASTM E-119) without cavity insulation at apanel thickness of ⅝″, installed on each side of a wall frame. Thesurface abuse resistance is measured by abrasion tests such as ASTMD4977-98b (Standard Test Method for Granule Adhesion to Mineral SurfacedRoofing) and also indentation tests such as ASTM D5420 (ImpactResistance of Flat, Rigid Plastic Specimen by Means of a Striker by aFalling Weight (Gardner Impact)). The panel impact resistance istypically measured by, for example, ASTM E695 (Measuring RelativeResistance of Wall, Floor and Roof Construction to Impact Loading), andISO 7892 (Vertical Building Elements—Impact Resistance Tests—ImpactBodies and General Test Procedures), or other suitable impact orabrasion tests.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013]FIG. 1 is a perspective view of a single piece laminate compositecomprising fiber-cement laminated to gypsum.

[0014]FIG. 2 is a cross-sectional view of the single piece laminatecomposite of FIG. 1, showing the fiber-cement and gypsum adheredtogether using an adhesive.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0015] The preferred embodiments of the present invention illustratedbelow describe a single piece laminate composite wallboard system. Itwill be appreciated, however, that the present invention is not limitedto wallboards, but can be utilized for any application where an abuseresistant, impact resistant and fire resistant building material isdesired.

[0016] As seen in FIG. 1, a preferred building material 40 is comprisedof a fiber-cement layer 10 laminated to gypsum layer 20, creating asingle piece laminate composite. FIG. 2 illustrates that the fibercement layer 10 may be laminated to the gypsum layer 20 using anadhesive 30, the thickness of which is exaggerated in FIG. 2 forillustration purposes, as described in further detail below. It will beappreciated that the fiber-cement and gypsum components can take anyform necessary, including, but not limited to, panels, sheets, skins,boards, or the like. In one preferred embodiment, the thickness of afiber-cement sheet 10 is between about {fraction (1/32)}″ and ¼″. Morepreferably, the fiber-cement sheet 10 is about ⅛″ thick, plus or minusabout {fraction (1/16)}″. A gypsum panel 20 typically has a thicknessbetween about ¼″ to ¾″, more preferably about ½″. It will be appreciatedthat other thicknesses for the fiber-cement sheet 10 and the gypsumpanel 20 may be used. The preferred weight is about 2.5 to 3 lbs/squarefoot, more preferably about 2.77 lbs/square foot for a ⅝″ thickcomposite wallboard.

[0017] One preferred embodiment of the invention is a composite panelthat is manufactured by bonding together a paper-faced ½″ type X gypsumwallboard to ⅛″ thick fiber cement panel. ASTM C 36 describes a type Xgypsum board to have not less than 45 minutes fire resistance rating forboards ½″ thick, applied parallel with and on each side of load bearing2″×4″ wood studs spaced 16″ on center with 6D coated nail, 1-⅞″ long0.095″ diameter shank, ¼″ diameter head, spaced 7″ on center with thegypsum joints staggered 16″ on each side of the partition and tested inaccordance with ASTM E 119. One preferred ½″ Type X gypsum panel is a ½″thick HARDIROCK® MAX “C”®, described in the table below. This gypsumpanel has an improved Type X fire resistance rated core and ismanufactured for commercial projects where building codes requirespecific levels of fire resistance and sound reduction. The ⅝″ thickboard is designed to provide greater fire resistance than standard FireX® board and achieves fire and sound rating with less weight.Application information is available in the Gypsum Association FireResistance Design Manual GA-600, Underwriter's Laboratories, Inc. FireResistance Directory. HARDIROCK ® MAX “C” ™ THICKNESS 1/2″ (12.7 mm)inches (mm) WIDTH 4′ (1219 mm) feet (mm) STANDARD LENGTHS 8′, 9′, 10′feet STANDARD EDGES Tapered or square APPROX WEIGHT 1.8 lbs/sq ft (8.8kg/m²) lbs/sq ft (kg/m²) ASTM SPECS C 36

[0018] It will be appreciated that the face of the gypsum panel 20bonded to the fiber-cement 10 does not necessarily require a paper face,and the gypsum panel 20 may be bonded directly to the fiber-cement 10. Apreferred gypsum panel 20 may also have a glass or polymeric fiber mator woven mesh combined into the panel on either the front or backsurface, either on the outside or the inside of the paper. This can bedone for two reasons. First, it can be used to improve the impactresistance of the gypsum panel 20 by itself. Second, it can be used toimprove the impact resistance of the gypsum panel as part of thecomposite wallboard 40.

[0019] The preferred composite wallboard 40 can be utilized in mostinterior wallboard installations. The preferred composite wallboard 40is installed such that the fiber-cement side of the wallboard 40 facesoutward to provide an abrasion and indentation resistant surface totraffic, and the gypsum side of the wallboard 40 is installed againstthe supporting framing, with the synergistic combination of thefiber-cement and the gypsum wallboard providing the fire resistancerating and strength of the panel. Neither the preferably gypsum panel ½″nor the preferably ⅛″ fiber-cement sheet 10 provides the 1-hour fireresistance rating in isolation, but rather the combination of the twomaterials in a laminated composite 40 has been tested in a symmetricalwall system and achieved a 1 hour fire resistance rating on a typicalsteel framing used in commercial building partitions. Results of a fireresistance test conducted on this composite panel are provided below.

[0020] The supporting framing is typically 20 or 25 gauge steel framing,or wood framing such as 2″×4″ Douglas Fir softwood. The wallboard 40 canbe fastened to the steel studs with suitable screws such as 6 gauge×1-⅛″Type S Bugle Head drywall or self-drilling screws. The wallboard 40 canbe fastened to wood studs with suitable nails or screws such as 1-¾″long cup-head gypsum wallboard nails or 6 gauge×1-⅛″ Type S Bugle Headdrywall screws. The preferred wallboard 40 is designed for use in wallassemblies that are subject to surface abuse and penetration. Such wallassemblies are typically found in schools, public housing, publicbuildings, interior garage walls, corridors, gymnasiums, change rooms,and correctional and healthcare facilities. The material can be cut witha carbide-tipped score and snap knife, power shears or circular sawoptionally with dust control.

[0021] Fiber Cement

[0022] The art of manufacturing cellulose fiber reinforced cement foruse in a fiber-cement sheet or skin 10 is described in the AustralianPatent AU 515151 and U.S. Pat. No. 6,030,447, the entirety of which isincorporated by reference. Fiber cement has the attributes ofdurability, resistance to moisture damage, low maintenance, resistanceto cracking, rotting or delamination, resistance to termites andnon-combustibility. Thus, the fiber cement layer 10 resists damage fromextended exposure to humidity, rain, snow, salt air and termites. Thelayer is dimensionally stable and under normal conditions will notcrack, rot or delaminate.

[0023] The basic composition of a preferred fiber-cement panel 10 isabout 20% to 60% Portland cement, about 20% to 70% ground silica sand,about 5% to 12% cellulose fiber, and about 0% to 6% select additivessuch as mineral oxides, mineral hydroxides and water. Platelet orfibrous additives, such as, for example, wollastonite, mica, glass fiberor mineral fiber, may be added to improve the thermal stability of thefiber-cement.

[0024] The dry density of a preferred fiber-cement panel 10 is typicallyabout 1.3 to 1.4 g/cm³ but can be modified by pressing the material todry densities up to 2.0 g/cm³ or by addition of density modifiers suchas unexpanded or expanded vermiculite, perlite, clay, shale or low bulkdensity (about 0.06 to 0.7 g/cm³) calcium silicate hydrates.

[0025] The flexural strength of a preferred fiber-cement panel 10,typically based on Equilibrium Moisture Content in accordance with ASTMtest method C 1185, is 1850 psi along the panel, and 2500 psi across thepanel.

[0026] A preferred fiber-cement panel 10 has a non-combustible surfaceand shows no flame support or loss of integrity when tested inaccordance with ASTM test method E136. When tested in accordance withASTM test method E84, a preferred fiber-cement panel 10 exhibits thefollowing surface burning capabilities:

[0027] Flame spread: 0

[0028] Fuel Contributed: 0

[0029] Smoke Developed: 5.

[0030] Lamination Process

[0031] A preferred panel is comprised of a ⅛″ nominal thickness fibercement sheet laminated to a ½″ thick type X fire resistant gypsum board.The gypsum panel is preferably manufactured with square edges. Anadhesive 30 as shown in FIGS. 1 and 2 above such as polyvinyl acetate(PVA) is spread over the surface of the gypsum panel and ⅛″ thick fibercement is placed over the surface and is typically pressed at about 38psi, in a stacked configuration, for approximately 30 minutes. Onepreferred adhesive is Sun Adhesives polyvinyl acetate (PVA) adhesive#54-3500 supplied by Sun Adhesives, a division of Patrick Industries.While the adhesive is most preferably a low cost adhesive such as PVA,other organic or inorganic adhesives may be used, such as water-basedpolymeric adhesives, solvent-based adhesives, thermoset adhesives,natural polymers such as modified starches, liquid moisture cure orreactive hot melt adhesives such as polyurethane, and heat or fireresistant adhesives.

[0032] The adhesive 30 is preferably applied by a roll-coater processwhereby the gypsum panel 20 is preferably cleaned to remove dust anddebris before the adhesive 30 is applied to the smooth face. Theadhesive 30 is preferably spread evenly over the entire surface of thegypsum panel 20. The wet film thickness of the adhesive 30, whenmeasured with a standard “wet film thickness gauge,” will preferably notbe less than about 4.5 mil and preferably will not exceed about 6 mil.The fiber-cement panel 10 is placed on top of the gypsum panel 20, whichis coated with adhesive 30, squared to the edges of the gypsum panel 20,and then stacked. The completed stack is preferably cured in a pressunder a load of about 37.5±2.5 psi for preferably no less than about 30minutes. The panels then preferably have the fiber cement surface sandedand the long edges machined with an abrasive wheel such as diamond gritto form a tapered edge. The machine sanding preferably utilizes threesanding heads. The grades of sanding belts preferably range from 40 gritto 220 grit. The long edges are machine tapered to allow for settingcompound, joint reinforcing tape and finishing compounds during flushjointing on installation. The surface of the product is preferablysealed with an acrylic emulsion to reduce the surface water absorptionto make it easier to paint and to improve paint adhesion.

[0033] The fiber-cement surface of the composite wallboard 40 may beoptionally sealed with an acrylic sealer such as UCAR 701 to facilitateon the job finishing. This can be achieved with a suitable latex paintwhich may be sprayed, rolled or brush applied for wallpaper or texturefinishes. It will also be appreciated that sanding the fiber-cementpanel 10 is optional in order to improve the finish of the fiber-cementsurface. Furthermore, it will be appreciated that sanding can be donebefore or after the fiber-cement panel 10 is laminated to the gypsumpanel 20. It will be appreciated that a roll press lamination processmay also be used, with a suitable pressure sensitive adhesive.

[0034] Testing

[0035] Abuse resistance tests were conducted on one preferred laminatecomposite panel. This preferred panel provided superior impactresistance to the common type X fire resistant gypsum wallboard. Thepreferred panel also has superior abrasion resistance to both the commontype X fire resistant gypsum wallboard and the abuse resistant gypsumbased panels.

[0036] A novel feature of the preferred embodiments of the presentinvention is that neither the ½″ gypsum wallboard or the ⅛″ fiber cementsheet, by themselves, provide altogether, the 1-hour fire resistancerating, surface abuse and impact resistance. However, laminating the twomaterials together provides the 1-hour fire resistance in a symmetricalwall system when tested to ASTM E119 and an improved level of surfaceabuse resistance and impact resistance.

[0037] It is believed that the preferred panel also has the advantagesof improved flexural strength and nail pull through strength and lesshumidified deflection compared to the individual components of thepreferred invention or a typical type X gypsum wallboard of the samethickness (⅝″ thick).

[0038] The preferred composite also has the novel features of fire andabuse characteristics in a single wallboard or a single piece system.Prior fire resistance rated and abuse resistant systems that utilizefiber cement required a two layer system over the supporting framework.There is considerable advantage with the preferred composite in reducedmaterial and quicker installation of a single piece system versus a2-layer system. The two layer system required installation of ⅝″ type Xgypsum wallboard followed by the installation of ¼″ fiber cement overthe top. The total thickness of these 2 layers adds up to ⅞″ of materialversus ⅝″ of material with the preferred laminated composite of thepresent invention.

[0039] Thus, in one embodiment the present invention provides a singlepiece system that is at least about one hour fire resistance-rated andabuse resistant. This reduces the amount of time to install compared tothe 2 layer system, lowers the mass of the wall unit per square footcompared to the 2 layer system, and requires less fixtures per wall forinstalling panel compared to the 2 layer system. Moreover, the materialis easily cut with power shears, which is a quick and easy method ofcutting.

[0040] The material also is abrasion resistant, indentation resistantand impact resistant (soft body and hard body), as illustrated in thetables below.

[0041] Surface-abuse and impact resistance can be determined by methodsused in such tests as ASTM D 4977-98b (Standard Test Method for GranuleAdhesion to Mineral Surfaced Roofing by Abrasion), ASTM D 5420 (ImpactResistance of Flat, Rigid Plastic Specimen by Means of a Striker by aFalling Weight (Gardner Impact)), ASTM E 695 (Measuring RelativeResistance of Wall, Floor and Roof Construction to Impact Loading), ISO7892 (Vertical Building Elements—Impact Resistance Tests—Impact Bodiesand General Test Procedures), or other suitable impact or abrasiontests. Fire resistance can be measured by tests such as ASTM E 119(Standard Test Methods for Fire Tests of Building Construction andMaterials), UL263, UBC 7-1, NFPA 251, ANSI A2.1, or other suitable fireresistance tests. One ⅝″ thick laminate composite embodiment, comprising⅛″ fiber-cement laminated on top of a ½″ Hardirock Max “C” Gypsum panel,achieved superior abrasion and impact resistance as illustrated in thetables below. TABLE 1 ASTM D4977-Wire Brush Surface Abrasion Test(Modified to have a total of 25 lbs load on brush) Abraded Depth AbradedDepth Product (mm) (inches) 5/8″ laminate composite 0.000 0.000 5/8″Type X Gypsum Board 0.016 0.001

[0042] TABLE 2 ISO 7892 Section 4.3-Hard Body/Impact Resistance Test(Single Impact @ 10 ft. Height-22 ft.-lb. force) Indentation IndentationDiameter Depth Product (inches) (inches) 5/8″ laminated composite 1.2700.275 5/8″ Type X Gypsum Board 1.788 0.275

[0043] The hard body impact test was conducted with a 1 kg ball bearingas outlined in Section 4.3.1 through 4.3.5 of ISO 7892.

[0044] The panels tested were fastened to 20 gauge steel framing withstuds at 16″ on center. The ¼″ fiber cement panel was fastened with 7gauge×1-¼ C-Drill screw spaced at 8″. The ⅝″ Type X gypsum wallboard wasfastened with 6 gauge×1-⅛″ Type S Bugle Head screws spaced at 8″ and the⅛″ fiber cement laminated on top of ½″ Hardirock Max “C” gypsumwallboard was fastened with 6 gauge×1-⅛″ Type S Bugle Head screws spacedat 12″. TABLE 3 ASTM D5420-Indentation Test/Gardner Impact Test ProductIndentation Dpeth (inches) 5/8″ laminated composite 0.101 5/8″ Type XGypsum Board 0.149

[0045] For the indentation test, ASTM D5420-96 Method GC was followedwhich specifies a 0.625 mm diameter striker orifice with a support platehole close to the diameter of the striker, and a 2 lb. weight falling adistance of 36 inches giving a single energy impact of (72±1.8) ft.-lbs.Ten specimens were tested from each product and values in the table havebeen averaged for all 10 TABLE 4 ASTM E675-79-Soft Body ImpactResistance Test Cumulative Impact Single Impact Force Force Product(ft.-lbs.) (ft.-lbs.) 5/8″ laminated composite 180 210 5/8″ Type XGypsum Board 60 90 ¼″ Fiber-cement Panel 60 90

[0046] The soft body impacter was fabricated according to therequirements of sections 5.2.1 through 5.2.4 of E695-79, filled to agross weight of 60 lbs. The bag is supported as a pendulum, striking thepanel midway between the stud and mid height of the test wall in 6″increments.

[0047] The cumulative impact was defined as the energy needed to reach“failure mode” either by “set deflection”, face/back cracking, and/orstud deformation of >0.25″. Upon reaching any of the previously definedfailure mode(s), the weighted bag was raised an additional 6 inches inheight to reach the “single impact energy” needed to reach a failuremode.

[0048] The cumulative impact was defined as the energy needed to reach“failure mode” either by: “set deflection”, and face/back cracking,and/or stud deformation of >0.25″. Upon reaching any of the previouslydefined failure mode(s), the weighted bag was raised an additional 6inches in height to reach the “single impact energy” needed to reach afailure mode.

[0049] The size of the panels was 4′×8′, and were fastened to 20-gaugesteel framing at 24″on center. The ¼″ fiber cement panel was fastenedwith 7 gauge×1-¼″ C-Drill screw spaced at 8″. The ⅝″ Type X gypsumwallboard was fastened with 6 gauge×1-⅛″ Type S Bugle Head screws spacedat 8″ and the ⅛″0 fiber cement laminated on top of ½″ Hardirock Max “C”gypsum wallboard was fastened with 6 gauge×1-⅛″ Type S Bugle Head screwsspaced at 12″.

[0050] Results in the table are an average of 3 panels of each materialtested.

[0051] Fire Resistance Testing

[0052] One embodiment of the present invention was tested for fireresistance according to ASTM E 119-98. This embodiment was tested as adual wall assembly, comprising a cold side and hot side. Each testassembly consisted of a 10 ft×10 ft non-loadbearing wall of 20 GA×3-⅝″steel studs spaced 24″ o.c. On the cold side, one layer of ⅛″ thickHardiboard® fiber-cement face skin laminated to ½″ thick Hardirock® “MaxC”® gypsum board was applied perpendicular (horizontally) to 20 GA.×3-⅝″steel studs 24″ o.c. with minimum 1″ long Type S drywall screws 12″ o.c.at floor and ceiling runners and intermediate studs. Fasteners wereplaced approximately 3″ in from panel comers and approximately ⅜″ infrom panel edges. On the fire side, one layer of ⅛″ thick Hardiboard®fiber-cement face skin laminated to ½″ thick Hardirock® “Max C”® gypsumboard was applied perpendicular (horizontally) to 20 GA.×3-⅝″ steelstuds 24″ o.c. with minimum 1″ long Type S drywall screws 12″ o.c. atfloor and ceiling runners and intermediate studs. Fire side horizontalpanel joints were offset from cold side horizontal panel joints by 24″.Fasteners were placed approximately 3″ in from framing comers andapproximately ⅜″ in from panel edges.

[0053] Framing members in fire-rated wall assemblies are cut ¾″ shorterthan full height of wall thereby creating a floating frame wall. Inorder to transport these walls from the fire test facility to the soundtest facility, fasteners were placed through the wall panels intoframing members at floor and ceiling runner tracks to provide rackingresistance to facilitate specimens handling. This modification does notchange the sound transmission characteristics of the wall assembly.

[0054] Joints were treated with chemically-setting powder gypsum jointcompound (USG® Durabond® 90), complying with ASTM Specification C 475,for flush joining the panel edges. Setting-type compound was mixed inaccordance with manufacturer's written instructions. Compound wasapplied to fastener heads and joint recess was formed by adjoiningsheets. Perforated paper reinforcing tape was immediately imbeddedcentrally into the joints. Perforated paper reinforcing tape wasimmediately imbedded with additional compound and allowed to dry.

[0055] The ambient temperature at the start of the test was 80° F., witha relative humidity of 84%. Throughout the fire test, the pressuredifferential between the inside of the furnace (measured at a point ⅓″of the way down from the top center of the wall specimen) and thelaboratory ambient air was maintained at −0.03 inches of water column,which resulted in a neutral pressure at the top of the test article.

[0056] Observations made during the test were as follows: Time (min:sec)Observation  0:00 Furnace fired at 8:52 a.m.  1:43 Applicant's laminatedcomposite panel separating out-of- plane (OOPS) at top horizontal jointon the fire side  2:20 Surface of Applicant's laminated composite panelcrack- ing and turning black  3:25 Laminate peeling and falling offexposed surface  4:15 Much of the laminate has fallen away; exposedgypsum paper flaming  7:13 Gypsum paper black/gray and flaking on fireside 10:30 All of the laminate has fallen off exposed surface 32:30˜1/8″ gap at the bottom horizontal joint on the exposed side 39:00 ˜1/2″OOPS at the bottom horizontal joint near center of wall on the exposedside. 60:00 The furnace was extinguished and the test article re- movedand exposed to the standard hose stream test. Hose Stream The wall wasexposed to the standard hose stream test for at a pressure of 30 psifrom 20 feet away, from the exposed surface for a period of 60 seconds.The test article failed the hose stream test when the hose streampenetrated the wall after 19 seconds.

[0057] During the fire test, the wall was measured for deflection atthree points along its vertical centerline: at 30″ (position #1), 60″(position #2) and 90″ (position #3) from the left side of the wall.Measurements were made from a taut string to the wall surface at eachlocation. Position TIME (min) #1 (in.) #2 (in.) #3 (in.)  0 5-3/8 5-3/85-1/2 10 5-5/8 5-5/58 5-7/8 20 6-1/4 6-1/2 6-1/2 30 6-3/4 6-3/4 6-7/8 406-1/2 6-1/4 6-1/2 50 6-1/4 5-7/8 6-1/4 60 6-1/4 6 6-1/2

[0058] Hose Stream Retest

[0059] In accordance with the standard, a duplicate specimen wassubjected to a fire exposure test for a period equal to one half of thatindicated as the resistance period in the fire endurance test,immediately followed by the hose stream test.

[0060] Observations made during the test were as follows: Time (min:sec)Observation  0:00 Furnace fired at 1:37 p.m.  0:53 Applicant's laminatedcomposite panel craking on the ex- posed side  1:20 Applicant'slaminated composite panel turning black  2:40 Gypsum paper turning brownwhere laminate has fallen off  3:00 Exposed gypsum paper ignited  4:25Exposed gypsum paper stopped flaming 11:00 Much of the laminate is gone,gypsum paper turning white 30:00 The furnace was extinguished and thetest article remov- ed and exposed to the standard hose stream test.Hose Stream The wall was exposed to the standard hose stream test for 60seconds at a pressure of 30 psi from 20 feet away from the exposedsurface. The test article withstood the hose stream test withoutallowing passage of water through the wall.

[0061] Conclusions from Fire Testing

[0062] The 20 GA., 3-⅝″ galvanized steel stud wall with Applicant'slaminated composite panels (⅛″ thick Hardiboard® fiber-cement face skinlaminated to ½″ thick Hardirock® “Max C”® gypsum wallboard) on bothsurfaces, constructed and tested as described in this report, achieved anon-loadbearing fire resistance rating of 60 minutes for a symmetricalwall assembly according to the ASTM E119 standard.

[0063] Summary of Advantages

[0064] The preferred embodiments of the present invention combine fireresistance of at least 1 hour and significant abuse and impactresistance in a prefabricated single piece laminate composite comprisingfiber-cement laminated to gypsum. These properties are achieved in alaminate composite which in one embodiment is only about ⅝″ thick thatis not excessively heavy, is easy to cut and is quick and easy toinstall.

[0065] One disadvantage of the two layer systems of the prior art isthat the individual pieces of fiber-cement and gypsum must beself-supporting in order to facilitate their individual installation.The layers of fiber-cement and gypsum, therefore, are limited in howthin they can be in order to remain self-supporting. The preferredembodiments of the present invention, however, combine the fiber-cementand gypsum layers into a prefabricated single piece laminate compositefor installation. Thus, the individuals layers of fiber-cement andgypsum need not be self-supporting, and the thickness of thefiber-cement layer, for instance, can be significantly reduced. Thisreduces the overall thickness of the single piece laminate composite ascompared to the two piece systems. As a result, one embodiment of thepresent invention incorporates a ⅛″ fiber-cement layer and a ½″ gypsumlayer to create a single piece laminate composite about ⅝″ thick, thatsimultaneously achieves a one hour fire resistance rating and abuse andimpact resistance.

[0066] The embodiments illustrated and described above are providedmerely as examples of certain preferred embodiments of the presentinvention. Various changes and modifications can be made from theembodiments presented herein by those skilled in the art withoutdeparting from the spirit and scope of the invention.

What is claimed is:
 1. A method of installing a composite buildingmaterial, comprising: positioning a composite building material adjacenta supporting frame, wherein the composite building material has twolayers, the first layer comprises gypsum and the second layer comprisesfiber cement, wherein the gypsum-containing layer is positioned againstthe supporting frame while the fiber cement-containing layer facesoutwardly from the supporting frame; and attaching the building materialto the supporting frame.
 2. The method of claim 1, wherein the buildingmaterial is attached to a metal supporting frame.
 3. The method of claim1, wherein the building material comprises a composite panel having athickness of about ⅝ inch.
 4. A method of installing a buildingmaterial, comprising: attaching a gypsum panel to a supporting frame,wherein the gypsum panel is about ½ inch thick; and attaching afiber-cement panel to an outer surface of the gypsum panel, wherein thefiber-cement panel is about ⅛ inch thick.
 5. The method of claim 4,wherein the fiber-cement panel is attached to the gypsum panel by anadhesive.
 6. The method of claim 4, wherein the building material isinstalled as an interior wallboard, wherein the fiber-cement panel ispositioned to face outward to the interior of a room.
 7. A method ofinstalling interior wallboards in a building structure, comprising:positioning a first interior wallboard adjacent a first side of asupport frame, wherein a first layer of the interior wallboard comprisesgypsum and a second layer of the interior wallboard comprises fibercement, wherein the second layer of the wallboard faces outward awayfrom the first side of the support frame; and attaching the interiorwallboard to the support frame.
 8. The method of claim 7, wherein the.interior wallboard is-about ⅝ inch thick.
 9. The method of claim 7,further comprising positioning a second interior wallboard adjacent asecond side of the support frame, wherein a first layer of the interiorwallboard comprises gypsum and a second layer of the interior wallboardcomprises fiber cement, wherein the second layer of the wallboard facesoutward away from the second side of the frame; and attaching the secondinterior wallboard to the second side of the support frame.
 10. Themethod of claim 7, wherein the support frame comprises load bearing woodstuds.
 11. The method of claim 7, wherein attaching the interiorwallboard to the frame comprises nailing the wallboard to the frame.